Beam tube switching circuits



0a. 21, 1958 v HO B E RG 2,857,552

BEAM TUBE SWITCHING CIRCUITS 2 Sheets-Sheet 1 Filed Sept. 13. 1954',

INVENTOR. GEORGE G HOBERG IN PUT SOURCE -78 ATTORNEY Oct. 21,1958

Filed Sept. 13, 1954 2 Shee ts-Sheet 2 25' 27' 29' DECADE use ' Fig.3 INPUT 78 SOURCE L 00o OUTPUT AND 7 (Moon OUTPUT Y GAT|NG BEAM g 0R PULSE 7 TUBE E v DECADE 0 EVEN INPUT v we. OUTPUT |55 "EVEN OUTPUT E INVENTOR.

GEORGE G. HOBERG ATTORNEY United States Patent rms 2,857,552

laterlted Oct. 21, 1958 2,857,552 BEAM TUBE SWITCHING cmcrnrs George G. Hoberg, Berwyn, Pa., assignor to Burroughs Corporation, Detroit, Mich, a corporation of Michigan Application September lS, 1954, Serial No. 455,546 13 Claims. (Cl. 315-21) plurality of target electrodes arranged concentrically,

Each of the target elecaround an elongated cathode. trodes is associated with a corresponding spade electrode used for locking the cathode ray beam in position upon its target electrode in a selected compartment. A magnetic field is created substantially parallel to the elongated cathode throughout the tube so that an electron beam I formed at the cathode of the tube will tend to follow a substantially equipotential path. For this reason the tubes are known as magnetron beam switching tubes. Means are provided including the spade electrodes to create an electrostatic field to establish a substantially i equipotential line from a particular target electrode to the cathode so that the electron beam will flow from the cathode to a single compartment defined by the said particular target. A small portion of the electron beam locks upon the associated spade electrode and reduces its potential by means of .a loadimpedance to thereby direct the remainder of the electron beam 'upon the corresponding target electrode.

Because of the magnetic field, the electron beam has a tendency to continuously rotate in a tight spiral around the cathode in one direction and would re-enter the cathode if it were not locked upon a particular spade electrode. When a substantially equipotential line is created between the cathode and the compartment adjacent to the compartment upon which the electron beam is impinging, the electron beam is caused to advance to the said adjacent compartment where it locks upon the spade electrode thereof. In some of the earlier tubes of this type locking may be accomplished by lowering the potential of either the spade electrode or the target electrode. A more recent developmentjhas resulted in the provision of a switching or control grid electrode in each compartment. Such tubes are described in" the copending application Serial No. 370,086 of Sin-Pin Fan and Saul Kuchinsky, filed July 24, 1953, now U. S. Patent No. 2,721,955. The switching electrode of one compartment, upon being reduced suificiently in potential, performs the function of establishing an equipotential path between the cathode and a spade electrode of an adjacent compartment to cause the electron beam to become locked in upon the adjacent compartment. If the potentials of successive ones of said switching electrodes are caused to assume a potential such as to establish an equipotential path between the associated compartment and the cathode, the electron beam will be caused to step consecutively from one compartment to the next. This has been accomplished in one manner by connecting one set of alternate "switching electrodes (hereinafter referred to as even numberedelectrodes) to one output terminal of a circuit'such' as'a flip-flopor binary 'of electronic circuitry.

, Z s V circuit and connecting the other setof odd numbered alternate switching electrodesto the other output of the flip-flop or binary circuit. Successive output pulses from the flip-flop circuit would then cause the electron beam to advance progressively from one compartment to the next.

A general object of the invention is toprovide improved electronic counters utilizing 'beam switching tubes of the type described hereinbefore.

An object of the present invention is to provide a system including a multiple position electron beam tube in which the electron beam maybe caused to step 'consecutively along its various positions in response to pulses applied to a single input terminal. c

Another object of the invention :is to provide a magnetron type electron beam switching tube system operable as a counter and having but a single input terminal for external signals to be counted.

In accordance with the invention, the groups of even and odd numbered target electrodes are respectively connected through impedance devicesto a supply potential. A feedback circuit is coupled from each impedance' device to one of the sets of odd or even numbered switching electrodes to thereby place the switching electrodes. in

a primed gating condition such that an external signal applied simultaneously to all of the switching electrodes will cause the beam to step only one position from' the target receiving the beam tothe next adjacent target. Thus, it is possible to step the electron beam from one target position to the next .with successive input signals by means of feedback circuits for partially gating the switching electrodes in response to beam current.

The system proposed by" the invention is particularly adapted for decimal decade counting with a minimum In decimal counters, therefore, common load impedance elements are u sed for allcommonly connected electrodes to. thereby simplify the associated switching circuitry. f j

Other objects and features of theinven'tion will be more fully understood from the following detailed description thereof when read in conjunction with the drawings, in which: c

Fig. l is a perspective assembly view of a multi-position magnetron beam switching tube utilized with the invention;

Fig. 2 is a schematic diagram of a counter embodiment incorporating the invention;

Fig. 3 is a schematic circuit diagram of a decimal decade counter circuit embodying the invention; and f Fig. 4 is a logical diagram of the circuit displayed in circuit Fig. 3.

Referring now to Fig. 1, there is shown a perspective view of a magnetron beam switching tube which is used in accordance with this invention.

This type tube is well known in the art, as evidenced by descriptions in publications such as Electronic. Design for January 1954; Consequently only a brief description will be given herein of the structure and theory of operation of the tube 9 of Fig. 1. The cathode 41 is positioned within the hermetically sealed envelope 10. A plurality of elongated spade electrodes 31 through'40, having a U-shaped cross section, are positioned concentrically about the cathode 41. Inthe structure shown in Fig. 1, there are ten such spade electrodes.

' Similarly, there are ten elongated target electrodes 11 through 20, having an L-shaped cross section, likewise positioned concentrically around the cathode 41,, and each associated with one ofthe-ten spade electrodes. Each targetwith its two adjacent spades definesaccmpartment for .receiving the beam in one oflits ten'stable locked in positions. Ten switchingelectrodes 21 through 30 are also positioned concentrically around the cathode I two functional groups.

ample, switching electrode-21 is positioned between the extending leg of spade electrode40 andthe open end of target electrode 11. The concentric magnet 42 placed l about the envelopelfliprrjduces a magnetic field in the tube that is substantially parallel to the elongated cathode 41. This magnetic field is of a polarity which will cause an electron beam extending outwardly from the cathode 41 to sweep around the tube in a clockwise direction (viewed from the top of the tube) in accordance with well known principles. 8 Each of the spade elec- Y trodes isadapted to lock the electron beam in a particular compartment by a lowering of its potential. The beam remains locked in by means of the electron beam fiowing through a spade impedance connected to the particular spadeelectrode upon which the electron beam is impinging thereby causing enough potential drop across said impedance to establish a substantially equipotential path somewhere between the two adjacent spade electrode and the cathode, thereby'causing the beam to impinge upon the target electrode. The switching electrodes perform the function of causing the electron beam to impinge upon the next consecutive spade electrode by distorting the electric field within a particular compartment to cause the'electron beam to advance to that spade electrode which willhold the beam in the compartment adjacent the one upon which it impinges in the absence of a switching potential. 'It is to be noted that when the electron beam is directed to a compartment that the electron 'beam is actually impinging upon both the spade electrode and the target electrode. The target electrodes normally receive most of the electron beam since only a small portion thereof is required to lock the electron beam upon a particular-spade electrode.

Referring now to Fig. 2, the various elements of the tube of Fig. 1, are presented in a different manner than in Fig. 1 in order to make the drawing more easily understood. More specifically the spade electrodes, the

target electrodes, and the switching electrodes are arranged in a straight line and further are separated into The group at the left of Fig. 2 consists consists of the odd numbered target electrodes 11',"'13, 17', and 19; the odd number spade elechaving the same unprimed reference character.

.Each of the odd numbered target electrodes 11', 13, 15, 17, and 19' is connected to a common power supply 'such as battery 87 through individual resistors 51 through 55 respectively. The junction of each taregt and associated resistor is connected to common junction point 74 through individual resistors 61 through 65 respectively. Likewise, the even numbered targetelectrodes 12, 14, 16', 18, and 20' are individually connected to the common battery 87 through the resistances 56 through 60 respectively and are connected to the common junction point 82 through resistances 66 through 70 respectively. The common junction point 74 is connected to ground through the series combination of resistance 71 and resistance 72 which constitute a voltage divider network. All of the odd numbered switching electrodes 21, 23, 25', 27, and 29 are connected to the junction point 92 between the resistance 71 and the resistance 72. Similarly, the common junction point 82 is connected to ground potential through the series combination of the resistance 83 and the resistance 85 which also constitute a voltage dividing network. The even numbered switching elec- 4 trodes 22', 24', 2 6', 28', and 30', are connected to the junction point 84 between the resistance 83 and the resistance 85.

The capacitors 73 and 81 which are connected across the resistances 71 and 83 respectively perform the function of increasing the time required for the potential of the junction points 74 and 82 to decrease when the electron beam impinges upon an odd or even target electrode. Junction points 92 and 84 are connected to a common junction point 76 for receiving an external signal through direct current blocking capacitors 75 and '79 respectively. Input pulse source 78 is connected to deliver a negative going input signal pulse at the common point 76 throughthe conductor 77. Each of the spade electrodes is connected to the common battery source 88 through a resistance individual thereto. As a specific example the spade electrode 31' is shown connected to the battery source 88 through the resistance 56. In order to avoid unnecessarily complicating the drawing, the resistors connecting the other spade electrodes to the common battery source 88 have been omitted.

From an inspection, it can be seen that each target electrode is connected to the battery source 87 through two principal impedance paths, the first being through the associated one of the impedances 51 through 60 and the second being through one of the remainder of the impedances 61 through 70 connected directly to the target electrodes. Specifically, for example, the target electrode 11' is connected to the battery source '87 through the resistance 51 and also is connected to the battery source 87 through the resistance 61 and resistances 5262, 53-63, etc. It is to be noted that common junction point 74 is positioned between resistance 61 and the resistance network set forth immediately above. The values of these resistances are so proportioned that the potential of the odd numbered switching electrodes are of a proper value to cause the electron beam to advance from an odd numbered target electrode to an even numbered target electrode when a pulse is transmitted from the input pulse source 78. The values of the potentials 'at various points in the circuit for one particular design are as follows:

V =2l volts E =lO0 volts V =250 volts V =60 volts V '=53 volts V =lOO volts V =l09 volts Where E is the target electrode battery source 87, E is the spade electrode battery source 88, and for the odd numbered group of electrodes wherein the electron beam is assumed to be impinging on the target electrode 11 V is the potential of the target electrode 11, V is the potential of the common junction 74 and V is the potential of the junction 92 to which the switching electrodes are connected. Likewisefor the even numbered electrodes V is the potential of the common junction point 82, V is the potential of the junction point 84 to which the even numbered switching electrodes are connumbered target electrode) be at a potential which will be lowered sufiiciently when an input pulse is applied to junction 76 fronrinput pulse source 7'8 to cause the electron beam to step to an even numbered target electrode and that the other set ofswitching electrodes (the even numbered set). be not lowered sufiiciently to cause the electron beam to continue stepping to the next following oddnumbered target electrode.

.when the electron beam is impinging on an odd numbered target electrode, the o'dd numbered switching electrodes It is to be noted that Assume that an electron beam voriginating at the ,cath

ode 41 is impinging uponthe target. electrode 11'. Assume further that it is desired to advance the electron beam two steps to target electrode 13. To do this the electron beam is first advanced'to the target electrode 12' which is physically located next adjacent the target electrode 11'. The electron beam is then advanced to the target electrode 13" which is next adjacent the target electrode 12. When the electron beam is impinging on the target electrode 11 the potential V of the junction 92 is 21 volts and the potential of the odd numbered switching electrodes which are connected to the junction 92 is also 21 volts. The potential 1,, of the junction point 84 and the even numbered switching electrodes is 53 volts since the electron beam is not impinging upon any of the seven numbered target electrodes. The potential threshold'of a. switching electrode which will cause the electron beam to advance from one target electrode to the next adjacent target electrode is about volts. The potentials of both junction point 92 and 84 in the absence of a pulse from inputso'urce 78 are above this threshold value'and consequently will notcause the electron beam to advance. Assume that a negative 20 volt pulse is transmitted from the input pulse source 78*to the junction point 76. Since the junction point 76 is. coupled to the junctions '92 and 84 through capacitors 75 and 79 respectively, the potential of the junctions 92 and 84 will be momentarily lowered by an amount'substantially equal to the value of the input pulse from input pulse source 78. Since the value of this input pulse is a negative 20 volts, the potential at junction 92 will become 1 volt and the potential at junction 84 will become 33 volts. It is to be noted that the potential of junction 92 which is connected to the odd numbered switching electrodes is below the 10 volt threshold potential whereas the potential of junction 84 which is connected to the even numbered switching electrodes is above the 10 volt threshold potential.

Therefore, it is possible to advance the electron beam in a tube of the type shown in Fig. 2 by lowering the potential of all the switching electrodes simultaneously for a duration of time shorterv than the time required for the electron beam to advance from a given target electrode to the next adjacent target electrode. If the potential of all the switching electrodes were lowered to switching potential for a greater period of time than the time required to switch the electron beam from one target electrode to an adjacent target electrode, the electron beam Would continue to rotate beyond the said adjacent target electrode. Consequently, it can be seen that if the potential of all the control grid electrodes were lowered to switching potential, the time interval of such lowered potentials must not be greater than the electron beam switching time interval.

In the circuit of Fig. 2 as the electron beam switches from target electrode 11 to target electrode 12, the even numbered switching electrodes will initially be at a potential higher than the potential required to cause the electron beam to advance since the electron beam current will have no substantial immediate effect on the potential 'of the target electrode 12 due to the capacitance 81 connected in the voltage divider circuit. Consequently, the electron beam will initially be unable to advance farther than the target electrode 12. However, the electron beam current will, in a later interval of time, cause the potential of the target electrode. 12' to decrease and thus cause the potential of the point 84 to decrease to a point Where, when added to the decrease in potential of the junction point- 84- caused by a. subsequent pulse from the input pulse source 78, the electron beam will be caused to advance to thetarge't electrode 13'. Thus, the switching of the beam from one position to another is made less critical.

It is to be specifically noted that since it takes 'a finite amount of time for the electron beam to lower the potential of the junction 84 to a value where an input pulse from source 78 would cause the electron beam to switch from the target electrode 12 to the target electrode 13', the maximum time duration permissible for an input pulse at junction 84 is greater bywthat aforesaid finite time than the otherwise maximum allowable time interval. Consequently, the input pulse requirements are not so highly critical that it is diflicult to operate equipment in the manner described. This is an important feature of the invention since it permits greater reliability and less original cost in pulse forming equipment.

Now that one pulse of the proper time duration and amplitude has been applied to the junction 76 from pulse source 78, the electron beam is impinging on target electrode 12. Conversely to the condition stated hereinbefore the odd numbered target electrodes are at the high potential and the even' numbered target electrodes are at the low potential. Consequently, when another input pulse .is applied to the junction 76 from pulse source 78, the even numbered switching electrodes will belowered below the threshold value to cause the electron beam to advance to the next adjacent target electrode 13' in the same manner. Subsequent pulses from the'source 78 willcause the electron beam to advance from one target electrode to another in like manner.

In the circuit of Fig. 3 similar reference characters have :been used where allowable to designate components of the nature hereinbefore described in the system of Fig. .2. Accordingly, those operational features hereinbefore discussed are immediately evident, and the description of this circuit will be limited to those elements which differ therefrom.

In this embodiment a single common load resistor 114 is used for coupling all of the odd targetelectrodes'to the battery source 87. Likewise, a common resistor 115 couples the even target electrodes to the battery source 87. In order to provide for decade output signals useful in coupling several of the decimal counter units of the type described in cascade circuit, a separate output terminal 108 is provided from the target electrode 19. In order to prevent an output signal response at the decade output terminal 108 as the beam impinges upon other odd numbered'target electrodes, the isolating or mixer rectifier device 110 is coupled between the impedance device 114 and the decade output terminal 108.

As in the hereinbefore described system, a signal developed in response to beam impingement upon either the odd or even sets of target electrodes, a signal is fed back to a corresponding set of switching electrodes by means of respective leads 91 and 86. Likewise an input source 78 is provided having such characteristics that both the input signal from the source at lead 77 and a coincident feedback signal from one of the target impedance devices 114 or 115 is required at one set of switching electrodes in order to enable the beam to step from one stable position to the next. The series diodes 112 and 119 are respectively connected from the input source 78 and the impedance element 114 to the coupling'capacitor 75. These diodes, together with resistor 111 and battery source 122, constitute a negative and circuit of the type well known in the art. Thus, a signal is not present at lead 91 unless both the required input signals are present in coincidence. This feature provides a favorable signal to noise ratio and permits greater tolerances upon the operating characteristics of the switching electrodes than otherwise available. and impedance 115 are coupled to leads 86 by respective diode elements 120 and 121.

In order to further stabilize the-operation of theswitch- In like manner, the source 78 v ing electrodes, particularly in view of the capacitor elements 75 and 79 which during discharge might tend to vary the potential thereof, a clamping circuit is provided for each set of switching electrodes. Thus, diode 141 and battery source 142 are coupled to the commonly connected set of odd numbered switch electrodes to maintain their potential at a clamped positive potential of proper value. Because of the orientation of the diode 141, the switching electrodes are free to travel in the negative direction to provide the switching function. A typical operational voltage for the clamp circuit is +30 volts. Under this operating condition the voltage divider network 14392 is such that the battery source 144 will normally cause the clamping diode 141 to conduct in the absence of input signal pulses at capacitor 75. Similar action takes place at the set of even numbered switching electrodes.

Fig. 4 illustrates in block form operation of the circuit of Fig. 3. Therefore, from the beam tube 150 the odd target output leads are connected through the or circuit 151 to be presented at the odd input leads 152 if arriving at the and circuit 153 in coincidence with a gating pulse at input lead 154. The separate decade output terminal 108 is available by separately taking a single target output electrode such as the ninth target through one rectifier of the or circuit 151. The even output electrodes are all commonly connected and are fed back by a single lead to the even input terminals by way of a similar and circuit 155. In this manner each of the successive series of gating pulses is able to cause the beam to step from one successive stable position to the next in a reliable manner.

Having therefore described the invention and its mode of operation, those features believed descriptive of its nature and scope are defined with particularity in the appended claims.

What is claimed is:

1. An electronic system comprising a multi-position beam switching tube having a beam forming structure, the tube having a plurality of beam receiving targets to accept the beam in any of its positions, the tube further having switching means to cause the beam to advance from one target position to another, means deriving a first gating potential from an electrode upon which the beam is impinging, an external source providing a second gating potential, and circuit means operating the switching means to cause the beam to switch from one target position to another only in response to both said gating potentials.

2. A system as defined in claim 1 wherein the tube has two alternate sets of switching elements and two corresponding sets of beam receiving electrodes, the circuit means comprises a coincidence circuit coupled to derive a first signal from one set of beam receiving electrodes to one set of switching elements, and further circuit means is provided coupling the coincidence circuit to derive a second signal from said external source.

3. A system as defined in claim 1 wherein the tube has two alternate sets of switching elements and two corresponding sets of targets, the circuit means comprises a coincidence circuit coupled to derive a first signal from one set of targets and a second signal from said external source, and adapted to deliver an output signal only in response to coincident input signals to the corresponding set of switching elements in such polarity and magnitude that the beam is caused to step from one target to another.

4. An electronic system comprising a multi-position electron beam switching tube, said multi-position electron beam switching tube comprising an elongated cathode and a plurality of compartments arranged concentrically around said elongated cathode, said plurality of beam receiving compartments comprising a set of even numbered electrodes and a set of odd numbered electrodes, each of said compartments defined by two adjacent elongated spade electrodes, one of the spades being adapted to cause the beam to impinge upon an associated elongated target electrode, and an elongated switching electrode adapted to cause the beam to move to the other of the spades, the plurality of elongated spade electrodes being positioned concentrically around said cathode and spaced a distance apart from each other, the plurality of target electrodes being positioned concentrically around said plurality of spade electrodes and spaced apart from each other and between two adjacent spade electrodes so that one each of said target electrodes will intercept a path from said cathode, the plurality of switching electrodes being positioned concentrically around said cathode and further individually positioned between individual ones of said plurality of target electrodes and the other of said spade electrodes, means to create a magnetic field substantially parallel to the cathode, a source of potential for said spade electrodes, a target potential source, a first target impedance device connecting each of a first set of target electrodes to said target potential source, a feedback circuit coupling said impedance device to a first set of switching electrodes, a further impedance device connecting each of the second set of target electrodes to said target potential source, afurther feedback circuit coupling the further impedance device to the second set of switching electrodes, and an input switching pulse source common to all of the switching electrodes.

5. A system as defined in claim 4 wherein said impedance devices for the target electrodes constitute the sole load impedance for all of the targets in the respective sets of target electrodes.

6. A system as defined in claim 5 including further means for coupling at least one of the target electrodes to an external circuit independently of the feedback circuit for producing an output signal.

7. A system a defined in claim 4 wherein the first set of target electrodes and the first set of switching electrodes are respectively located within the same beam receiving compartments.

8. An electronic switching system comprising a multiposition electron beam switching tube including an electron-emitting cathode and a plurality of groups of electrodes surrounding said cathode; said groups of electrodes including beam-holding electrodes, target electrodes, and beam-switching electrodes; and a feedback connection from a plurality of said target electrodes to a plurality of said beam-switching electrodes.

9. An electronic switching system comprising a multiposition electron beam switching tube including an electron-emitting cathode and a plurality of groups of electrodes surrounding said cathode; said groups of electrodes including beam-holding electrodes, target electrodes, and beam-switching electrodes; all of said electrodes being connected in two separate sets; and a feedback connection from the target electrodes of each set to the switching electrodes of the same set.

10. The system defined in claim 9 and including a common signal source coupled to both sets of electrodes.

11. An electronic switching system comprising a multiposition electron beam switching tube including an electron-emitting cathode and a plurality of groups of electrodes surrounding said cathode; said groups of electrodes including beam-holding electrodes, target electrodes, and beam-switching electrodes; alternate ones of said groups of electrodes being designated odd electrodes and the others of said groups of electrodes being designated even electrodes, the odd target electrodes being connected together, the odd grid electrodes being connected together, the even target electrodes being connected together, the even grid electrodes being connected together; a first current feedback path from said even targets to said even grids; a second current feedback path from said odd targets to said odd grids and a signal source coupled to each of said feedback paths.

12. An electronic switching system comprising a multiposition electron beam switching tube including an electron-emitting cathode and a plurality of groups of electrodes surrounding said cathode; said groups of electrodes including beam-holding electrodes, target electrodes, and beam-switching electrodes; a feedback connection from a plurality of said target electrodes; a signal source; and a coincident circuit coupled to said feedback connections and to said signal source and having an output connection to a plurality of said grid electrodes.

13. An electronic switching system comprising a multiposition electron beam switching tube including an electron-emitting cathode and a plurality of groups of electrodes surrounding said cathode; said groups of electrodes including beam-holding electrodes, target electrodes, and beam-switching electrodes; said target electrodes and said beam-switching electrodes being connected together in two sets; a feedback connection from said target electrodes of each set to said beam-switching electrodes of the same set.

References Cited in the file of this patent UNITED STATES PATENTS 

